This invention relates to improvements in operability of differentials, and particularly to improvements in limited slip differentials, wherein a substantial driving torque may be provided to both driving wheels of a road vehicle, regardless of loss of traction by one of the wheels.
Limited slip differentials having means for limiting or preventing normal differential action are well known. For example, U.S. Pat. No. 2,855,805 illustrates and describes a face coupling assembly for transmitting torque between one of the side gears of a differential and its associated axle shaft. The face coupling functions to move working components of the differential unit to positions which resist normal differential action. Axial thrust is developed via the use of positive pressure angles on mating surfaces of the face coupling and the side gear, whereby imbalances in driving torque in the side gears result in the biasing of the face coupling against conventional locking means. There is, however, no means within the conventional limited slip differential for varying the bias ratio of the unit which could be, for example, provided by the use of non-constant pressure angles in the mating surfaces of either the side gear or face coupling, respectively. As the bias ratio represents the ratio of non-slipping wheel torque to slipping wheel torque, a variable bias ratio is seen as desirable in a multitude of applications, ranging from off-road equipment to various two and four wheel drive highway vehicles.